Combustion Optimization Of Coal To Liquid Diesel Based On Oxygenated Fuel And Injection Strategy

In order to alleviate the energy crisis and environmental pollution and promote the development of the internal combustion engine industry,it is urgent to develop diversified clean energy.Aiming at the energy structure of "rich coal,poor oil and little gas",studying and developing coal-to-oil technology can not only enhance the utilization rate of coal resource,but also fill the oil gap in our country,ease the role of dependency on oil.In addition,under the background of "Carbon peaking and carbon neutrality goals",the efficient and clean utilization of coal to liquid diesel in compression-combustion engines has become a topic of wide concern to researchers.In this paper,based on the Jilin Provincial Natural Science Foundation project,the optical engine test platform independently built by the research group,combined with high-speed photography and two-color method,is used to study the combustion process of coal-based synthetic diesel in the engine and the process of carbon smoke generation.Further,through the joint control of oxygen-containing fuel and injection strategy,the way of realizing efficient and clean combustion of coal to liquid diesel in compression-combustion engine is explored,which provides theoretical basis and technical support for the promotion and application of coal to liquid diesel.The main research contents and conclusions are as follows:(1)Direct Coal-to-Liquids(DCTL),China Ⅵ vehicle diesel and Indirect Coalto-Liquids(ICTL)are selected as base fuels.The influence law of coal-based synthetic fuel on engine combustion and soot generation was investigated.The results show that the higher cetane number of ICTL results in a larger proportion of diffusion combustion,a higher flame area and brightness,and a higher soot generation compared with conventional diesel.DCTL has low cetane value and late ignition time,but because of its good volatility,the proportion of pre-mixed combustion in the combustion process is larger,the temperature gradient in the cylinder is lower,and the carbon smoke generation is less.(2)By adjusting injection timing and pressure,further explore the influence of injection strategy on combustion and soot generation of coal-based synthetic diesel oil.The results show that with the increase of injection advance Angle,the flame area and brightness of ICTL and DCTL,as well as the amount of soot produced,both increase first and then decrease.Meanwhile,the flame brightness and area of fuel gradually decrease with the increase of injection pressure,the temperature distribution in the cylinder becomes more uniform,the number of pixels with KL factor >0.06 of soot decreases,and the amount of soot produced decreases.Through comparison,it is found that the change of injection strategy has a significant effect on ICTL combustion process and soot generation process,but has limited potential to improve the temperature field distribution and soot generation of DCTL fuel.Therefore,under the premise of ensuring engine power,increasing injection advance Angle and injection pressure is beneficial to improve the combustion of ICTL and reduce the generation of soot.(3)Aiming at the problem of excessive carbon fume generation during ICTL combustion,oxygen-containing fuels(n-butanol,DMC and PODE3)were selected as additives to prepare mixed fuels(BC,DC and PC)by mixing with ICTL,and the effects of different oxygen-containing functional group structures on engine combustion and carbon fume generation characteristics were explored.The results showed that the flame area and peak brightness decreased obviously(ICTL>PC≈BC>DC)after mixing oxygen-containing fuel into ICTL,and the time of obvious flame was delayed in different degrees.The sequence was ICTL,PC,BC,DC.In addition,because the local BC flame is less than ICTL and PC,the temperature distribution in the combustion process is more uniform,and the KL factor pixel point is the lowest at each crankshaft Angle,n-butanol has the most prominent effect on improving the combustion of ICTL and inhibiting the formation of carbon smoke among the three oxygenated fuels.(4)ICTL with different n-butanol mixing ratios were selected as test fuels to further explore the effects of n-butanol mixing ratio on combustion and carbon smoke generation.The results show that the flame area and brightness gradually decrease with the increase of n-butanol mixing ratio.When the proportion of n-butanol exceeds20%,the area of high temperature area >1600K in the cylinder almost disappears,the number of KL factor >0.06 pixels decreases to zero,and the carbon smoke production decreases.(5)ICTL and ICTL(B10)mixed with 10% n-butanol were selected as experimental fuel to explore the effects of injection timing on combustion and soot generation.The results show that the ignition time of B10 moves forward with the advance of the injection time.The flame area and brightness in the combustion process increase first and then decrease,and reach the peak value when the injection time is 9°CA BTDC.In addition,when injection time is the same,ICTL high temperature area and KL factor pixel number are higher than B10 fuel.This indicates that the combined regulation of mixing n-butanol fuel and increasing injection advance Angle has a more significant effect on improving ICTL combustion temperature and inhibiting carbon smoke generation.